Preparation of AlOOH/Al2O3 porous ceramics having CO2/N2 gas selectivity of less than 1

Porous Al2O3 bodies, having an average pore size of approximately 74 nm and a porosity of 40.4%, were prepared by the slip-cast method. The intended porous ceramics were prepared by hydrothermal treatment of the porous Al2O3 bodies. The obtained samples consisted of AlOOH and α-Al2O3 phases, and the α-Al2O3 surfaces were coated with AlOOH particles. The CO2/N2 gas selectivities of the samples depended on the conditions of the hydrothermal treatment and were found to decrease with increasing hydrothermal treatment time. However, the gas selectivities of the samples heated for 96 h were nearly equivalent to those of the samples heated for 72 h. A high concentration of Al(NO3)3, which was used as the aluminum source, leads to a decreased CO2/N2 gas selectivity. Moreover, CO2/N2 gas selectivity decreased slightly at low pressure drop. The minimum selectivity attained was approximately 0.69 at 0.02 MPa.